The 34-inch Hewitt Camera

Aperture 860mm, 680mm focal length, f/1

The 34-inch Hewitt Camera, situated in Dome C is not open to the public but the dome may be accessed on some Open Evenings when the 16-inch Meade telescope is in use.

The Hewitt camera was designed by Joseph Hewitt in the 1950s for use in tracking ‘Blue Streak,' a British ballistic missile which was then under development. When the ballistic missile programme was cancelled in 1960 it was decided to use the Hewitt design to track satellites. Two cameras were built and became operational in 1962, one in Evesham, Worcestershire (becoming known as the ‘Malvern' camera) and one in Lye Vallets, Herefordshire. The optics of the instruments is that of the ‘Schmidt Camera' which combines good light-gathering power with a wide field of view. The spherical focusing mirror is 864mm (34-inches) in diameter and has a focal length of 680mm (26.77-inches). The correcting plate with a diameter of 630mm (24.80-inches) was placed 1062mm (41.81-inches) from the front surface of the mirror, at or near its centre of curvature and gave an effective focal ratio of f/1. A field flattening lens, placed in front of the photographic plate allowed a flat photographic plate to be used instead of the curved ones usually required by the Schmidt design. Thus the camera was equipped to take high precision photographs of a significant part of the satellite's trajectory, together with enough bright background stars to give reliable positional references. In 1982 the ‘Malvern' camera came to Herstmonceux and proceeded to take 3300 spherical images which were used to record the tracks of artificial satellites passing overhead. Each image covered an area of sky approximately 20 times the width of the full Moon (10 degrees). Analysis of the satellites orbit gave information about the Earth's gravity field and the properties of the upper atmosphere.The second camera moved to Siding Springs in New South Wales, Australia and operated from 1982 to 1990, providing results to complement those obtained at Herstmonceux.

The Hewitt camera and the 16-inch Meade

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